Design issues in telecommunication blade systems and their resolution through design of experiments

There is an increasing need for improved node density and better power efficiency in telecommunication market. In addition, the telecommunication server environment also requires rugged high system performance systems with compliance to rigorous standards. Hence, the design of telecommunication blade servers presents several conflicting electrical and mechanical parameters in terms of desired transmission frequencies, blade density, energy utilization, and total cost. The blade chassis is a compact, high-density, highly modular, rack mount scalable server system with support for twelve single-wide server blades. The telecommunication system was designed to house existing (and future) blade servers and switch modules from standard enterprise blade server systems. This created some mechanical and electrical design challenges for the high-speed telecommunication blade server system. Enterprise blade servers are typically designed for blade chassis with a mid-plane as the vehicle for communication through a set of redundant fabrics. In order to conform to this mechanical requirement, an additional interposer and novel flexible cable structure had to be used which increased the length of the high-speed links and it added additional discontinuities to the link topology while still achieving the same high-speed date rates. In this paper, the effects of design parameters such as trace characteristic, printed circuit board (PCB) material characteristics, connector type and flexible cable utilization are effectively analyzed in the context of the electrical and mechanical specifications and the link speed requirements. A comprehensive modeling and simulation technique based on design of experiments (DoE) is presented that effectively addresses the electrical design issues at the pre-layout stage of the design. A selective set of routing guidelines was developed based on comprehensive sets of modeling and simulation scenarios that represented the worst case interconnect topologies for each design case representing all supported fabric technologies. A comprehensive modeling and simulation technique is presented that effectively addresses the electrical design issues and it optimizes the overall system design. Hardware and modeling results are presented and correlated in this paper.